After injection, the final axonal concentration of α-synuclein was estimated to be ∼7–13 μM, which is approximately two to four times greater than measurements of endogenous α-synuclein at synapses and commensurate with overexpression levels in mammalian PD models and human patients (Singleton et al., 2003; Miller et al., 2004; Nemani et al., 2010; Scott et al., 2010; Westphal and Chandra, 2013). The gene discussed is SNCA; the disease is Parkinson disease.